vhd: if we discover an unexpected Batmap version, report the found version rather than the expected

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
lwt: if we attempt an unaligned I/O print the bad alignment

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
vhd: the latest Batmap version we understand is 1.2

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
vhd: round up the Batmap_header to a sector boundary

Signed-off-by: David Scott <dave.scott@eu.citrix.com>